This invention relates to gas lasers and in particular, to a new and improved discharge electrode assembly for rapid gas displacement in a very low inductance electrically pumped gas laser operating in a fast repetitively pulsed mode. The electrode assembly should provide for gas flow control, electrical discharge initiation and maintenance, cooling, and positive displacement of the laser gas across the discharge gap for effective waste product removal. These functions are achieved with the new and unique flow through electrode arrays of the present application.
A flow through electrode array should provide a smooth flow pattern through the discharge gap at very high flow rates and provide rapid removal of the waste discharge product and rapid removal of the waste heat from the laser cavity for operation in high repetition rate, high power pulsed electrical laser applications.
For an important class of pulsed electrical lasers commonly referred to in the literature as "pulsed electrical lasers of the self-terminating type" (G. G. Petrash, "Pulsed Gas-Discharge Lasers," Soviet Physics USPEKHI, Vol. 14, No. 6, May-June, 1972, pp. 747-765), high power and efficient laser generation can only be achieved in very high current but very low inductance electrical discharge circuits since the discharge current rise time and pulse duration must be sufficiently short in comparison with the spontaneous emission life time of the upper laser state so as to avoid premature termination of population inversion (and hence laser action). For electronic transition gas lasers operating in the ultraviolet, visible, and near infrared parts of the electromagnetic spectrum, the spontaneous emission life time of the upper laser state lies typically in the range of 10.sup.-.sup.8 to 10.sup.-.sup.7 second (that is, one/one hundred millionth to one/ten millionth of a second). To achieve high current electrical discharge with current rise time and pulse duration lying in this range, it is generally necessary to employ a very low inductance electrical energy storage system (capacitors) which is closely coupled to the discharge chamber with good impedance matching. A good example of how such electrical coupling can be achieved through the use of an integrated double-parallel-plates transmission line energy storage/discharge circuit in a high power pulsed nitrogen laser design configuration is given in a recent paper -- Jeffrey I. Levatter & Shao-Chi Lin, "High-Power Generation from a Parallel-Plates-Driven Pulsed Nitrogen Laser," Applied Physics Letters, Vol. 25, No. 12, Dec. 15, 1974, pp. 703-705.
Gas lasers have been used with honeycomb electrode configurations for operation at low pressure (typically below 1 torr) in the glow discharge mode. However such electrode configuration is not suitable for operation at moderate to high gas pressures (a few torr and up) above the low gas pressures which correspond to glow discharges, nor for operation in high voltage pulsed modes. Such configuration is also not suitable for adaptation in a high current, very low inductance electrical discharge circuit for efficient generation of pulsed lasers of the self-terminating type as mentioned in the preceding paragraph. In another known device, a plurality of rods or wires is supported parallel to the flow path to serve as electrodes. These wire shaped electrodes provide no flow smoothing and have minimum surface contact with the flowing gas for effective heat transfer and do not permit any electrode shaping for positive control of the electrical discharge current distribution in the high current pulse mode.
None of the known prior art electrode assemblies provide the desired performance and accordingly it is an object of the present invention to provide a new and improved discharge electrode assembly particularly suited for fast electrical rise time, high repetition rate, high power pulsed electrically pumped gas lasers and providing gas flow control with smooth flow patterns, electrical discharge initiation, cooling, and removal of waste products from the laser cavity for maintenance of good laser performance at high pulse repetition rates.